The RHV region of S-RNase in the European pear (Pyrus communis) is not required for the determination of specific pollen rejection.

Zisovich, Annat H.; Stern, Raphael A.; Sapir, Gal; Shafir, Sharoni; Coldway, Martin

In the gametophytic self-incompatibility system, growth of self-pollen tubes in the style is inhibited in a haplotype-specific manner by S-RNase. The mechanism by whichS-RNase confers its specificity is unknown. However, a hypervariable region (RHV in Rosaceae and HVa-HVb in Solanaceae) that differs among the many cloned S-RNase alleles has been proposed to be involved in conferring theS-haplotype specificity of the S-RNase. Region swapping experiments between S-RNases and crystallography of the enzyme support this assumption. However, the deduced amino acid sequences ofSn-RNaseandSi-RNasealleles from the European pear (Pyrus communis) were recently found to have an identical RHV. In the present study it is shown that Sn-RNase does not prevent fertilization bySi-pollen haplotype, thus presenting a case in which RHV is not required for the determination of specific pollen rejection by S-RNase, and implying that other regions in the enzyme may be sufficient for this specificity.

PEARS; POLLEN; CRYSTALLOGRAPHY; ENZYMES; AMINO acid sequence; AMINO acid analysis

Sexual Plant Reproduction, 2004, Vol 17, Issue 3, p151

0934-0882

Academic Journal

10.1007/s00497-004-0225-9